Kate (Poesy) and Justin (Campbell Moore) live in the upstairs flat of a London house. Thirty-something, successful and affluent, they are expecting their first baby. All appears well on the surface though Kate harbours deep-rooted fears about her fitness to be a mother and her ability to love her child. One day, another couple, Jon (Morrissey) and Theresa (Laura Birn), move in to the empty apartment below. They are also expecting a baby and, in stark contrast to Kate, Theresa is full of joy at the prospect of imminent motherhood. Pregnancy brings the women together in a blossoming friendship as Kate becomes entranced by Theresa’s unquestioning celebration of her family-to-be. Everything changes one night at a dinner party in Kate and Justin’s flat. Kate begins to sense that all is not as it seems with the couple below. Then a tragic accident throws the couples into a nightmare and a reign of psychological terror begins.